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Quick answer. For most UK pilots, the right detector is an active unit with a clear attention-getting warning, dependable power, a practical sensor life and an alert that can be noticed while wearing a headset. Aviation-specific products such as the Moxy LFS-2601 and Sensorcon AV8 Inspector are strong options to compare. A suitable commercial off-the-shelf active detector may also be acceptable under the CAA route, but it still needs to be appropriate for the aircraft, operation and cockpit environment.
This is a research-based comparison, not a hands-on product test. Specifications can change, and a product listing is not proof that a detector is approved for every aircraft or operation. Check the latest CAA documents, manufacturer instructions, aircraft documentation and operator requirements before relying on any device.
Why carbon monoxide deserves attention in light aircraft
Carbon monoxide is colourless and odourless. In a piston-engine aircraft it can enter the cabin through exhaust-system defects, heater systems or gaps and seals. Early exposure can cause headache, dizziness, tiredness, nausea or poor concentration. Those effects are especially dangerous in flight because they can impair judgement before the pilot realises what is happening. Many pilots first encounter piston-engine cockpit safety in a common trainer; see Learning to Fly in a Cessna 172 for a beginner’s view of the aircraft and pre-flight routine.
An active detector does not prevent a leak. It provides an early warning so the crew can follow the aircraft checklist, increase ventilation when appropriate, isolate cabin heat if required, use oxygen if available, and land as soon as safely possible. The aircraft manufacturer’s procedures and current CAA guidance take priority over any general summary in a buying guide.
What the UK CAA rule requires
From 1 January 2025, operators of applicable piston-engine aircraft are required to carry a functioning active carbon monoxide detector when flying with passengers who do not hold a recognised pilot qualification. The rule has exemptions and conditions, so pilots should read the current version of Safety Directive SD-2024/001 (Version 3 at the time of writing) and CAA Safety Sense Leaflet 34 rather than relying on a shortened description. In summary, the directive applies to UK-registered aircraft and to foreign-registered aircraft flying in UK airspace; single-seat and open-cockpit aircraft are exempt, as are aircraft with wing-mounted engines unless cabin heat comes from an exhaust heat exchanger or combustion heater. Flights where everyone on board holds a recognised pilot qualification do not need a detector, although the CAA still recommends one.
The CAA accepts both aviation-standard equipment and commercial off-the-shelf active detectors as routes to compliance. That does not make every detector suitable, nor does it mean a household product is automatically ‘CAA approved’. The operator still has to choose, position, test and maintain a functioning device that gives an effective attention-getting warning.
Passive colour-change spot cards are useful only as a possible backup. They do not actively attract the pilot’s attention and should not be treated as the main detector where the active-detector requirement applies.
The detectors worth comparing
| Option | Best suited to | Alert approach | Important limitation | Where to buy |
|---|---|---|---|---|
| Moxy LFS-2601 | Pilots prioritising alerts through the headset | Spoken headset alerts with additional indicators | No live numerical ppm display; confirm plug and aircraft compatibility | Moxy (UK manufacturer) |
| Sensorcon AV8 Inspector | Pilots wanting a compact live ppm monitor | LCD, LED and 80 to 85 dB buzzer; Pro adds vibration | UK availability and future sensor service should be checked | Check price on Amazon.com |
| TOCSIN 4 | Pilots wanting multiple physical alert modes | Backlit ppm display, audio, flashing light and vibration | Primarily a specialist import; verify service and calibration arrangements | Specialist pilot shops (e.g. Sporty’s) |
| Radiant CO-Pocket | Pilots wanting a small rechargeable aviation unit | Display, bright visual warning and buzzer | Manufacturer says the buzzer may not be heard in a noisy cockpit; sold as supplemental | Radiant and its stockists |
| FireAngel FA3322 | Pilots considering a readily available UK COTS unit | Colour LCD, low-level monitoring and 85 dB alarm | Domestic and leisure-vehicle product, bulkier and not designed specifically for aviation | UK electrical and DIY retailers |
Prices and stock change frequently, so we link to the retailer rather than quoting a price. Our Amazon links go to the US store (Amazon.com), so prices show in US dollars; UK buyers should check delivery, import charges and the seller before ordering. Always confirm the current model, sensor life and seller before buying.
Moxy LFS 2601
Moxy is a UK-available aviation-specific detector designed to put spoken warnings directly into the pilot’s headset. This tackles one of the biggest cockpit problems: a standalone buzzer may be difficult to hear through an active-noise-reduction headset. It uses an electrochemical sensor, provides staged warnings and runs from a replaceable 9V alkaline battery. For more on ANR, PNR and cockpit audibility, read The Best Aviation Headsets Under $500.
The trade-off is that Moxy does not provide a live numerical ppm display. It also sits in the audio path, so buyers must check headset plug compatibility, aircraft connections and operator requirements. For a pilot who values an unmistakable voice warning more than a live number, it is one of the most interesting UK options.
Moxy sells direct through its UK website, and some UK pilot shops also stock it.
Sensorcon AV8 Inspector and Inspector Pro
The AV8 Inspector is a compact aviation monitor with a live LCD reading, 1 ppm resolution, visual indicators and an audible alarm. The stated low and high alarm points are 35 ppm and 200 ppm. The Pro version adds vibration and adjustable features, which may make it easier to notice in a noisy cockpit.
Its clear numerical display is useful for noticing trends rather than waiting for a high-level alarm. Check current stock, battery requirements and the manufacturer’s sensor-life or service arrangements before buying.
- AVIATION CO MONITORING – Real-time CO readings from 0-500 ppm for pilots, ground crew, maintenance technicians, and insp…
- INDUSTRIAL and SCIENTIFIC APPLICATIONS – Trusted by pilots, flight schools, ground crew, aviation maintenance technician…
- HANDS-FREE IN THE COCKPIT – Compact lightweight design with steel clip, lanyard loop, and optional removable panel mount…
- AVIATION CO MONITORING PRO – Real-time CO readings from 0-500 ppm with user-programmable alert thresholds and vibration …
- INDUSTRIAL and SCIENTIFIC APPLICATIONS – Trusted by pilots, flight schools, ground crew, and aviation maintenance profes…
- PROGRAMMABLE ALERTS WITH VIBRATION – Set custom low and high CO alert thresholds. Triple notifications: audible, visual …
TOCSIN 4 cockpit monitor
The TOCSIN 4 combines a backlit ppm display with flashing light, vibration and a loud audible warning. That mix is valuable because no single warning method is perfect in every cockpit. It is also more rugged than many domestic alarms. The drawbacks for a UK buyer are specialist availability and the need to understand the sensor-replacement or factory-service process.
The TOCSIN 4 is mainly sold through specialist pilot shops such as Sporty’s; UK buyers should confirm shipping and how sensor service is handled before ordering.
Radiant CO Pocket
Radiant’s CO-Pocket is a compact rechargeable unit designed for aviation use. It displays carbon monoxide concentration, temperature and humidity and adds a bright red visual warning. The manufacturer describes it as a supplemental, non-TSO and non-PMA device and warns that its buzzer may not be audible in a noisy cockpit. That makes positioning the display where it can be seen particularly important.
See the Radiant CO-Pocket product page for current stockists.
FireAngel FA3322 as a COTS option
The FireAngel FA3322 is a mainstream UK carbon-monoxide alarm with a colour display, low-level monitoring, an electrochemical sensor and a sealed 10-year battery. It is certified for domestic premises and leisure accommodation, not designed specifically as an aviation product.
The CAA permits suitable active commercial off-the-shelf detectors, so a product in this category can be worth considering. However, buyers should not translate that general allowance into a claim that this individual model is CAA approved. Consider its size, temperature range, mounting, visibility, alarm behaviour and audibility in the actual cockpit.
The FA3322 is widely stocked by UK electrical and DIY retailers; see FireAngel’s product page for specifications.
Integrated alternatives
Some higher-cost aviation products include carbon-monoxide detection as one feature. Examples include the Lightspeed Delta Zulu headset and ForeFlight Sentry or Sentry Plus portable receivers. These can be sensible if you already need a premium headset or compatible electronic-flight-bag receiver, but they are expensive ways to obtain CO detection alone. If you are weighing a headset upgrade anyway, our guide to aviation headsets under $500 explains passive and ANR options. Check app, region, traffic and weather compatibility before treating an integrated product as the best-value choice.
Seven features that matter more than the brand name
An active warning. Choose audible, visual, vibration or headset-routed alerts that actively attract attention. Multiple modes provide useful redundancy.
An alert you can notice with your headset on. A loud specification measured in a quiet environment does not guarantee the alarm will cut through engine noise and ANR. Test the detector’s own alarm function before flight.
A useful threshold. CAA guidance considers 50 ppm an appropriate warning threshold, while allowing lower-sensitivity choices. Understand what the device displays and when it actually alarms.
Live concentration display. A ppm display can reveal a rising trend and help with diagnosis, but only if it remains visible to the pilot and is not relied on instead of an active warning.
Sensor life and calibration. Electrochemical sensors age. Check the end-of-life indication, calibration policy and whether the sensor can be replaced locally or requires factory service.
Dependable power. Compare replaceable, sealed and rechargeable batteries. Add battery or charging status to the pre-flight check, and carry the specified spare battery when appropriate.
Safe positioning. Secure the detector so it cannot become a loose object, block controls or obstruct the view. Follow the manufacturer’s airflow and placement instructions.
How to use an active detector responsibly
A detector should be treated as part of the pre-flight and maintenance routine, not a gadget left in the bottom of a flight bag. Before use, confirm that it powers on, completes its self-test and shows the expected normal indication. Learn the alarm pattern before flight, check the battery or charge state, and record sensor replacement or calibration dates.
If the unit has a live display, place it in the pilot’s normal field of view while respecting its airflow guidance. If it relies primarily on sound, test whether the alert is perceptible with the headset and cockpit noise environment you use. Never expose a detector to exhaust gas simply to test it unless the manufacturer specifically provides a safe procedure.
CO detection supplements good maintenance. Exhaust systems, cabin heaters, firewalls, seals and associated components still require inspection and prompt attention when defects are suspected.
Find maintenance support and pilot shops
A detector warns you about carbon monoxide; it does not find or fix the source. If you suspect an exhaust, heater or seal problem, or simply want your aircraft’s exhaust and cabin-heat system looked at during routine maintenance, a qualified maintenance organisation is the right place to start. Our guide on how to choose an aircraft maintenance shop explains which UK approvals to look for.
- Browse Aircraft Maintenance & Services in the AviatorFinds directory to find maintenance organisations and engineers by location.
- Browse Pilot Gear & Aviation Shops for retailers that stock cockpit safety equipment, spare batteries and replacement sensors.
What to do if the alarm activates
Treat an alarm or rising reading seriously. Follow the aircraft flight manual, checklist and current CAA procedure. Typical priorities include increasing fresh-air ventilation, turning cabin heat off when appropriate, using supplemental oxygen if available, considering the condition of everyone on board, advising air traffic services, and landing as soon as safely possible. Do not continue simply because the reading falls; the source still requires investigation before further flight. New pilots may also find Aircraft Radios Explained useful for understanding ATC communication and emergency calls.
Frequently asked questions
Is a carbon monoxide detector mandatory in every UK light aircraft?
No. The active-detector requirement applies to specified piston-engine aircraft and operations, particularly when carrying passengers who do not hold a recognised pilot qualification. Exemptions and definitions matter, so check the current Safety Directive and Safety Sense Leaflet 34.
Can a household carbon monoxide alarm comply?
The CAA permits suitable commercial off-the-shelf active detectors as an acceptable route. Suitability is not automatic: assess the warning threshold, attention-getting alert, temperature range, mounting, power, sensor life and cockpit audibility. Do not describe a model as CAA approved unless the CAA explicitly says so.
Is a colour-change spot card enough?
Not where a functioning active detector is required. A passive card does not provide an audible, visual electronic or vibrating warning. It may serve as a backup but should not replace the active unit.
Where should the detector be placed?
Follow the manufacturer’s instructions. A real-time display should be visible to the pilot, the sensor needs suitable airflow, and the device must be secured away from controls and exits. Avoid placing it where a vent could produce a misleading local reading unless the manufacturer directs otherwise.
How often should it be replaced or calibrated?
There is no single interval for every detector. Follow the manufacturer’s sensor-life, end-of-life, battery, self-test and calibration instructions. Put the relevant dates in the aircraft or flight-bag reminder system.
Which type should you choose?
Choose Moxy if headset-delivered warnings are the priority and the connection suits your aircraft. Choose an AV8 Inspector or TOCSIN-style monitor if you want a dedicated live ppm display and several alert modes. Consider a carefully assessed COTS unit if UK availability and low ownership effort matter most. Choose an integrated headset or receiver only when its other functions justify the additional cost.
Whichever route you take, the best detector is the one that is suitable for the operation, correctly positioned, within its sensor life, powered, tested and capable of getting your attention before carbon monoxide affects your ability to fly.
Ready to choose a detector?
Compare the options in the table above, check the current CAA guidance, then pick the unit whose alert you will actually notice with your headset on.
Run a maintenance organisation or pilot shop? Add or claim your free AviatorFinds listing so pilots can find you, or see Premium listing options.
Official guidance and product information
UK CAA carbon monoxide in general aviation guidance
UK CAA Safety Directive SD-2024/001: Active carbon monoxide detectors
UK CAA Safety Sense Leaflet 34: Carbon monoxide safety
Moxy LFS-2601 manufacturer information
Sensorcon AV8 Inspector manufacturer specifications
FireAngel FA3322 manufacturer information
